Treatment of alkyl aromatic hydrocarbons with a hypochlorous acid compound in the production of sulfonate detergents



United States Patent Herman S. Bloch, Chicago, and George L. Hervert, Downers Grove, 11]., assignors to Universal Oil Prodl ucts Company, Chicago, 111., a corporation of Delaware No Drawing. Application April 2, 1951, Serial No. 218,892

This invention relates to a process for treating alkyl aromatic hydrocarbons intended as starting materials in the production of detergents to thereby reduce their color 2 Claims.

and odor and enhance the detergency of the detergent product prepared therefrom. More specifically, the present invention concerns the treatment of said alkyl aromatic hydrocarbons prior to their conversion to detergent products with a hypochlorons acid compound selected from the acid itself or an alkaline salt thereof.

In the production of alkyl aromatic hydrocarbons intended as starting materials for the manufacture of detergents, particularly the mono-alkyl substituted benzene hydrocarbons in which the alkyl group contains from about 9 to about 18 carbon atoms per group, which are particularly suitable as starting materials in the production of the corresponding alkyl aromatic sulfonate detergents, the alkylate is usually colored, varying from light yellow to deep shades of tan and the product contains partially oxidized impurities having an undesirable rancid odor. In a subsequent conversion of the alkylate to detergent, for example, by sulfonation followed by neutralization of the resulting sulfonic acid, the colored and odoriferous impurities are carried over into the final detergent product and depreciate the economic value of the detergent by decreasing its acceptability by the consuming public. Furthermore, it has been observed that the undesirable color and odoriferous impurities in the alkylate tend to reduce the yield of detergent manufactured therefrom in the subsequent conversion of the alkylate to the detergent product; conversely, it has likewise been noted that the alkylate treated in accordance with the method herein specified produces a significantly greater yield of detergent product than an alkylate which has not received the present treatment prior to its conversion to the detergent. While no specific reason for the observed improvement can at present be positively stated and no definite mechanism for the reactions involved can be set forth, it is believed that the treatment of the alkylate with the present treating agent comprising a hypochlorons acid compound in liquid phase converts the undesirable impurities to organic compounds lacking the undesirable properties of the impurities originally present in the alkylate or to organic compounds soluble in the aqueous phase, thereafter removed from the immiscible alkylate hydrocarbon phase by separation of the respective phases.

The primary object of the present invention, therefor, is to improve alkyl substituted aromatic hydrocarbons from the standpoint of color, odor and reactivity of the hydrocarbon in subsequent detergent producing conversion reactions. Another object of the invention is to provide a simple,'but efiective, method for treating an alkyl aromatic hydrocarbon suitable for ultimate conversion to a detergent product, whereby its color and odor are improved and more desirable detergent products may be prepared therefrom.

In one of its embodiments, the present invention concerns a process for treating a long chain alkyl substituted aromatic hydrocarbon in which the alkyl group contains from about to about 18 carbon atoms per group which comprises mixing said hydrocarbon with an aqueous solution of a hypochlorons acid compound selected from the group consisting of hypochlorons acid and a salt thereof at substantially non-chlorinating reaction conditions.

A more specific embodiment of .theinvention relates 80 to a process for improving the color, odor and reactivity of an alkyl substituted benzene hydrocarbon in which one of the alkyl substituents contains from about 9 to about 18 carbon atoms per alkyl group which comprises mixing said hydrocarbon with from about 1 to about 10 volumes per volume of said hydrocarbon of an aqueous solutlon of sodium hypochlorite containing from about 0.5 to about 5 pounds of available chlorine per pounds of said solution at a temperature of from about 0 to about 70 C.

Other objects and embodiments of the present invention relating to specific aspects thereof such as charging stocks, processing conditions, and other factors involved in the present process will be referred to in greater detail in the following further description of the invention.

Suitable alkyl aromatic hydrocarbons utilizable as charging stock in the present process which may advantageously be treated by the present method are in general selected from the above class of hydrocarbons intended as intermediates in the ultimate production of products wherein colored and odoriferous impurities are a decided disadvantage, as in the case of alkyl aromatic hydrocarbons intended for the manufacture of detergents which are marketed to the general consuming public. Alkyl aromatic hydrocarbons of the latter class produced by alkylation procedures in which the colored and odoriferous impurities are normally produced in the usual operation of the alkylation process are either the monocyclic or polycyclic aromatic hydrocarbon series containing alkyl groups having at least five carbon atoms per group, such as amylnaphthalene, nonylnaphthalene, amy1dimethyl naphthalene, dodecylbenzene, dodecyltoluene, pentadecylbenzene, octadecylbenzene, nonyltoluene, hexyltoluene, and other long chain alkyl substituted benzene and polycyclic aromatic hydrocarbons containing a single long chain alkyl group and one or more short chain alkyl groups such as methyl and ethyl substituents.

Alkyl aromatic hydrocarbons containing a long chain nuclearly substituted alkyl group which provides the hydrophobic portion of the detergent molecule essential for detergency of the ultimate product are produced synthetically by alkylation of an aromatic hydrocarbon having a nuclearly substitutable hydrogen atom such as benzene or toluene, with an olefin-acting alkylating agent such as a long chain olefinic hydrocarbon, generally in the presence of an acidic condensation catalyst, such as liquid hydrogen fluoride or substantially anhydrous hydrofluoric acid, sulfuric acid, aluminum chloride and other acid-acting condensation catalysts well known in the alkylation art. Alkylates which are particularly adapted to the present method of treatment are the long chain alkyl benzenoid hydrocarbons in which the long chain alkyl group contains from about 9 to about 18 carbon atoms per group, formed by alkylation of benzene or toluene with an olefinic hydrocarbon containing from about 9 to about 18 carbon atoms per molecule. It is believed that the impurities present in the alkylate product which are responsible for the odor and color thereof are indirectly produced during the alkylation reaction and although undesirable in the subsequent use of the alkylate, are nevertheless an unavoidable component of the product, at leas insofar as the presently known methods of alkylate production have been developed. The impurities apparently accompany the desired alkylate fractions in the distillation of alkylate product and cannot be separated therefrom by mere fractionation techniques in accordance with present distillation procedures. Decolorization with activated adsorb ents, such as activated charcoal, is not only costly from the standpoint of the initial expense of the activated adsorbent, but the latter also carries with it a substantial amount of valuable alkylate which cannot be recovered therefrom except by costly recovery procedures. The present method of treatment, on the other hand, involves merely mixing the hydrocarbon alkylate phase with the aqueous hypochlorons acid or hypochlorous acid salt solution under conditions sufiicient to obtain an intimate dispersion of the immiscible alkylate phase in the aqueous solution, thereafter permitting the phases to separate by settling, and recovering the upper alkylate phase from the aqueous layer, for example, by decantation. Initial mixing of the immiscible phases may be effected by any suitable means, for example, by merely stirring, shaking or otherwise agitating the liquids in a suitable vessel, by passing the liquids through an orifice mixer or by other means well known in the art.

The treating agent utilized in the present process may be supplied to the mixing or treating zone as an aqueous solution containing from about one to about ten Weight per cent of available chlorine per unit weight of solution. This. available chlorine may be in the form of hypochlorous acid or it maybe an essentially neutral or slightly basic solution or suspension of a hypochlorous acid salt. Thus, a dilute aqueous solution of sodium hypochlorite, formed by dissolving gaseous chlorine in aqueous sodium hydroxide or other basic sodium compound comprises one of the preferred forms of supplying the treating agent of the present invention to the process flow. Another utilizable form of treating agent in the present process is a suspension of commercial bleaching powder or calcium hypochlorite or the aqueous solution recovered by decantation of the aqueous layer from a mixture of the bleaching powder in water. In general, it is preferred to utilize from about one to about five volumes of water per volume of alkylate as the carrying medium for the hypochlorous acid or hypochlorite salt.

The desired objects of the present method of treatment are realized utilizing as little as 0.5 pounds of available chlorine per 100 pounds of alkylate, although greater decolorization and more thorough removal of the odoriferous impurities from long chain alkyl aromatic hydrocarbon alkylates are obtained by utilizing slightly greater quantities of available chlorine, for example, from about 0.5 to about 1.5 pounds per 100 pounds of alkylate. As an illustration, an alkylate of initially yellow color (-11 Saybolt), upon treatment with 0.5 pounds available chlorine per 100 pounds of alkylate is raised in Saybolt color to about +14 (as determined by a standard Saybolt Universal Chromometer). Slightly greater quantities of available chlorine, for example, 0.6 to about 0.8 pounds of available chlorine per 100 pounds of alkylate are capable of raising the Saybolt color to about 17 to 20. Contact periods of the alkylate with the aqueous hypochlorous acid or hypochlorite salt of from about 10 to about 160 minutes (and preferably about 60 to about 100 minutes) at reaction conditions characterized as substantially non-chlorinating conditions, generally at temperatures of from about to about 90 C. and preferably from about 50 to about 80 C., are in general suitable ranges of operating conditions within which the present treatment of the alkylate is effected. The reaction variables may be controlled within rather wide limits, however, to adapt the process to particular charging stocks and available apparatus.

The charging stock from which the color and/or odor is to be removed may be treated by any suitable procedure whereby intimate contact between the aqueous treating agent and charging stock is obtained and may be subjected repeatedly to successive charges of treating agent until the desired reduction in color is obtained. Thus, the aqueous treating agent and immiscible alkylate charging stock may be contacted by countercurrent flow of the respective liquids through a suitable treating tower which may contain a packing material such as quartz chips, Berl saddles, etc. to enhance interfacial contact-between phases. The aqueous hypochlorous acid compound may also be added to the alkylate in small increments with heating or cooling between increments, if desired.

The present invention is further illustrated with respect to specific embodiments thereof in the following examples, which, however, are not intended to limit the scope of the invention in strict accordance therewith.

Example I Detergent alkylate formed by alkylating benzene with a propylene polymer fraction boiling from about 170 C. to about 225 C. (containing 95+%, propylene tetramer) in the presence of concentrated sulfuric acid at a temperature of 0 C. was fractionally distilled to separate a predominantly dodecylbenzene fraction boiling from about 270 to about 325 C. The above distillate fraction had a distinct yellow color which was approximately Saybolt -11 by determination in a Standard Saybolt Chromometer in accordance with the standardized procedure for this instrument. Redistillation of the alkylate yielded a distillateof substantially the same color, having a Saybolt color.

The colored alkylate fraction was shaken with about 2 volumes of a dilute aqueous solution of hypochlorous acid (formed by bubbling chlorine into water at 20 C.) containing approximately 0.4% available chlorine (about 1 lb. of available chlorine/100 lbs. of alkylate). The aqueous phase at 25 C. was shaken with the alkylate for ten minutes, the color of the resulting separated alkylate being improved to a Saybolt color of +4. After 20 minutes of shaking, the Saybolt color of the alkylate was +12. After 30 minutes shaking, the Saybolt color was +14. An additional 30 minutes of shaking produced an alkylate the color of which was Saybolt +15. The Saybolt color number increased by 1 for each additional 40 minutes of mixing until a total of 180 minutes and then increased only slightly for additional much longer periods of mixing. The recovered alkylate sulfonated to the extent of 98.5% of theoretical, the sulfonic acid derivative of which when neutralized with aqueous caustic and dried formed a light cream-colored detergent product. By comparison, the untreated alkylate sulfonated only to the extent of and the resulting sulfonic acid intermediate when neutralized and the resulting salt dried yielded a tan-colored detergent salt product having a characteristic disagreeable odor undesirable for household detergent use. The volume percent recovery of alkylate from the treating operation was over 99%.

Example II The alkylate product (principally dodecylbenzene) produced as in Example I was treated with an aqueous solution of sodium hypochlorite. The alkylate was shaken initially for 30 minutes with 2 volumes of the hypochlorite solution containing a total of 0.2 lb. of available chlorine per 100 lbs. of alkylate at a temperature of 66 C., the operation reducing the color of the recovered alkylate from a Saybolt color of 11 to a Saybolt color rating of -1. The recovered alkylate layer was then shaken for 30 minutes with an additional 2 volumes of aqueous sodium hypochlorite containing 0.4 lb. of available chlorine per 100 lbs. of alkylate at a temperature of 66 C. The recovered alkylate layer had a Saybolt color rating of +17 and amounted to over 99 volume percent re.- covery. Its organic chlorine content was less than 0.05%. When the treated alkylate was sulfonated, the sulfonic acid neutralized with aqueous caustic and the resulting aqueous alkyl aromatic sulfonate dried, a detergent salt was produced which was substantially white in color and had no detectable odor.

We claim as our invention:

1. In the production of sulfonate detergents. by sulfonation of hydrocarbon alkylates comprising an aromatic hydrocarbon having an alkyl group of from about 5 to about 18 carbon atoms, the method of improving the detergent with respect to color and odor and increasing the reactivity of the alkylate in sulfonation which comprises mixing with the liquid alkylate, prior to. the sulfonation thereof, an aqueous solution of a compound selected from the group consisting of hypochlorous acid and a salt thereof, thereafter stratifying the mixture into a liquid alkylate phase and an aqueous layer, and separating the alkylate phasefrom the aqueous layer.

2. In the production of sulfonate detergents by sulfonation of hydrocarbon alkylates. comprising an aromatic hydrocarbon having an alkyl group of from about 5 to about 18 carbon atoms, the method of improving the detergent with respect to. color and odor and increasing thereactivity of the alkylate in sulfonation which comprises mixing with the. liquid alkylate, prior to the sulfonation thereof, an aqueous hypochlorite solution. containing from about 0.5. to. about 5' lbs. of available chlorine per 100. lbs. of said' alkylate, said solution being in an amount of from about 1 to about 10 volumes per volume of the alkylate and the mixing being at a temperature of from about 0 to about 90 C., thereafter stratifying the mixture into a liquid alkylate phase and an aqueous layer, and separating the alkylate phase from the aqueous layer.

References Cited in the file of this patent UNITED STATES PATENTS 1,945,121 Savell Jan. 30, 1934 2,021,740 Egloff et al. Nov. 19, 1935 2,232,761 Balthis, Feb. .25 1941 2,333,830 'Toone Nov- 9... 1943 2,581,117" Love Jan. 1', 1952 

1. IN THE PRODUCTION OF SULFONATE DETERGENTS BY SULFONATION OF HYDROCARBON ALKYLATES COMPRISING AN AROMATIC HYDROCARBON HAVING AN ALKYL GROUP OF FROM ABOUT 5 TO ABOUT 18 CARBON ATOMS, THE METHOD OF IMPROVING THE DETERGENT WITH RESPECT TO COLOR AND ODOR AND INCREASING THE REACTIVITY OF THE ALKYLATE IN SULFONATION WHICH COMPRISES MIXING WITH THE LIQUID ALKYLATE, PRIOR TO THE SULFONATION THEREOF, AN AQUEOUS SOLUTION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF HYPOCHLOROUS ACID AND A SALT THEREOF, THEREAFTER STRATIFYING THE MIXTURE INTO A LIQUID ALKYLATE PHASE AND AN AQUEOUS LAYER, AND SEPARATING THE ALKYLATE PHASE FROM THE AQUEOUS LAYER. 